1. Field of the Invention
The present invention relates to minimizing data retrieval time and/or area, or more particularly, to a system and method for minimizing read-only data retrieval time and/or area by using combinatorial logic to provide read-only data to a requester.
2. Description of Related Art
Electronic circuits typically operate in conjunction with at least one form of memory. For example, a personal computer generally includes a central processing unit (CPU) that operates in conjunction with random-access memory (RAM) and read-only memory (ROM)—the major difference being that RAM can both store and retrieve user defined data whereas ROM can only retrieve data established at the time of manufacture.
Typically, RAM is constructed by dividing a read/write portion of memory into discrete address bits, thus allowing data to be stored at, and retrieved from, a particular address location. For example, in response to a computer user providing a data-processing program (e.g., Word, Word Perfect, etc.) with the word “dog,” the program might temporarily store the word in RAM at a particular address location (e.g., address one-thousand). If the document is subsequently printed, the program will retrieve the word “dog” from the previously stored address location (e.g., address one-thousand) and provide it to the designated printer.
As well, ROM, regardless of its limited use (in that it cannot store user provided data), is typically constructed in the same fashion. A read-only portion of memory is divided into discrete address bits to allow read-only data to be retrieved from a particular address location. For example, a Pentium processor, which uses load constant instructions, may retrieve these constants from a particular address location in ROM—these constants being established at known addresses in the ROM module at the time of manufacturing.
The benefit of similar construction is that all forms of data—both stored and manufacturer established (i.e., read-only) data—can be retrieved by merely providing the memory module with the address location at which the data is located. The disadvantage of using such a similar construction is that both memory modules take roughly the same amount of time to execute (i.e., roughly an entire clock cycle), and utilize the same amount of real estate to store a single bit of data. In other words, ROM, which is more simplistic (in terms of read/write) than RAM, takes approximately the same amount of time to execute an instruction (i.e., provide data), and uses the same amount of area (per bit), as RAM.
This becomes especially problematic when the read-only memory (ROM) is small in comparison to the random-access memory (RAM), because a relatively large amount of time (usually an entire clock cycle) is needed to differentiate between a relatively small amount of manufacturer established data (i.e., the read-only data stored in ROM). Thus it would be desirable to have a system and method that minimizes read-only data retrieval time and/or area for ROM devices.